Cytosine-gated hole creation and transfer in DNA in aqueous solution

Abstract

The underlying mechanism of charge generation and transfer in DNA is of fundamental importance to the understanding of freeradical-induced damage 1,2 and the development of both molecular electronic and biosensor devices. 3 Oxidatively generated damage to DNA by radical attack and absorption of ionizing radiation leads to selective strand cleavage at guanine (and multi-guanine) sites through the migration of electron-loss centers (holes) in DNA. 4 It is known from measurements of ionization potentials, IP, that the purine bases in isolation are more easily oxidized than the pyrimidine bases, 5 and theoretical gas-phase calculations give the order of ease of oxidation as guanine,G > adenine,A . cytosine,C > thymine,T. 6 This has been borne out in aqueous solution where the measured value for the one-electron reduction potential of the guanyl radical (for guanosine), E(G¥ , H+ /G), is 1.29 V compared to the radicals of adenosine (1.42 V), 2′-deoxycytidine (ca. 1.6 V), and thymidine (ca. 1.7 V).